net_sched: export pfifo_fast prio2band[]

pfifo_fast prio2band[] is renamed to sch_default_prio2band[]
and exported because we want to share it in FQ.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Dave Taht <dave.taht@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>